1. Field of the Invention
This invention relates to a hydraulic device, such as a swash plate type hydraulic pump and a swash plate type hydraulic motor.
2. Description of the Prior Art
There is a known hydraulic device of this kind, which comprises a cylinder block fixedly mounted on a rotary shaft rotatably supported on a frame, a plurality of plungers slidably fitted in the cylinder block and arranged circularly around and concentrically with the axis of rotation thereof, a swash plate mounted on the frame in an inclined manner with respect to the rotary shaft in opposing relation to the plungers, the plungers being in abutting engagement with the inclined surface of the swash plate through universally rotatable shoes such that the plungers are moved reciprocatingly along the surface of the swash plate by the rotation of the cylinder block, or alternatively the cylinder block is rotated by the reciprocating movements of the plungers along the surface of the swash plate. The shoes in this hydraulic device, which are moved slidingly on the inclined surface of the swash plate, contribute to the smooth movements of the plungers along the surface of the swash plate.
In the conventional hydraulic device of this kind, the shoes are provided separately for the respective plungers and are adapted to move in the radial direction in accordance with an angle of inclination of the swash plate. Therefore, the shoes are sometimes caused to float from the slide surface of the swash plate or vibrate due to the fluctuations of hydraulic pressure in the interior of the cylinder block. The floatation and vibration of the shoes cause wear on various component parts of the device, noises and a decrease in the operation efficiency. To avoid these problems, it is known to provide a holding plate on the rear surfaces of all of the shoes. However, it is very difficult to manufacture such a holding plate with high tolerance that can be securely placed uniformly into abutting engagement with the rear surfaces of all of the shoes. Accordingly, no satisfactory results can be obtained.